Air-pressure indicator for pneumatic tires.



R. IVI. EVANS. AIR PRESSURE INDICATOR FOR PNEUMATIC TIRES. APPLICATION FILED 0CT.30I 1916.

1199971@ Patented 11111131.1918.

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ROBERT M. EVANS, or SEATTLE, wAsH'INGToN.

AIR-PRESSURE INDICATOR FOR VPNEUMA'JIG TIRES.

Specification of Letters Patent.vv

rammed nee. ai, Tais.

` Application led October 30, 1916. Serial No. 128,388.'

To all whom t may concern:

Be it known that I, ROBERT M. EVANS, a citizen of the United States, residing at Seattle, in the county of King and State of Washington, have invented certain new and useful Improvements in Air-Pressure `Indicators for Pneumatic Tires, of which the following is a specification.

This invention relates to air-pressure indicating devices for pneumatic tires, and has for its object the provision of a pressure indicator of simple construction that may be applied and indefinitely maintained in operative connection with a tire inlet valve whereby the variations in air pressure within the tire may be observed at all times; and is particularly adapted to indicate when the pressure'has fallen below a predetermined minimum of safety whereupon the tire may be supplied with additional air before any damage is caused from traveling upon aninsuliiciently inflated tire.

The invention consists in the novel construction of an air pressure indicator, and its combination and adaptation of parts, as will be fully described in the following specification, illustrated in the accompanying drawings, and finally set forth in the appended claims.

In said drawings, Figure 1 is a view in vertical section of an air pressure indicator embodying my invention shown attached to a tire valve shell.

F ig. 2 is a fragmentary view in side elevation on a reduced scale, of an automobile wheel with my indicating device attached thereto.

Referring to said views, the reference numeral 1 indicates a pneumatlc tire which is mounted upon the wheel rim 2 in the shell. The lowerI exterior portion of the" casing is screw-threaded to receive a nut 8 which casing isy which is in air-tight connectionv wit-hthe tire rim 2 through annular gasket 10.

A block 11 is exteriorly screw-threaded,v

whereby it may be secured in threaded engagement with the screw-threads 6 at adjusted positions within the interior of the casing 5 and is formed with an axially arranged bore 12. The lower end of said bore is enlarged, as at 13, to receive the reduced neck 15 of the tire valve shell. At the upper end of said enlarged portion of the bore a rubber gasket 16 is positioned to forni an air-tight Joint at this point, with the upper end of said neck 15.

A tripping device, as 17, is provided in said bore, to engage the valve stem 18 of a valve in the tire valve shell 3, whereby the same is opened simultaneously with the operative securement of the indicator casing with the tire valve shell.

The block 11 is formed with a boss 20 upon its -end opposite its engagement with the tire valve, to which an expansible air chamber 21 is fixedly secured, as by solder. Said air chamber is desirably formed of metal, and is provided with a plurality of vexpansion cells 22 whose upper and lower walls 23 constitute diaphragins against which the air pressure existing with- 1n said cells expands more or less inv longitudinal directions, as will be clearly understood from an inspection of the drawings.

Superimposed upon said air chamber is a plate 25 having a centrally disposed integral stem 26 extending outwardly axially of the casing and arranged to -protrudxe therefrom through an aperture 27 when the pressure of air in said air chamber is suiiciently great. A

A disk 28 is pressed into the end of said casing, having an aperture 30 to receive said stem 26 and a downwardly extending boss 31 whereby a coil-spring 32 is centered which has its opposite end disposed to bear upon said plate 25.

rEhe apertures 27 and 30 may bot-h be formed by boring into the end of said casing after the disk 28 yis pressed into its seat, as y shown, whereby said apertures maybe-most reliably alined and a close sliding fit readily made with said stem.

Adjustments of the block 11 axially of the casing may be easily and quickly made through a transverse slot 83 which is formed upon the bottom of said block and which is other similar tool to by a screw driver or lscrew-- the block in either direction to adjust the tension placed adapted. to be engaged \upoi i said spring 32.

A set screw 35 is arranged to protrude through the wall of said casing and impinge upon the peripheral surfacey of said block,

whereby said block may be maintained in set positions. a

Positioned longitudinally within the interior of said air-chamber 21 is a tubular member 36 having its lower end supported upon the upper' surface of the boss 20 and its upably proportioned per end extending in proximity to the upper portion of said air-chamber' to serve as a stop to limit the inward travel of the air-chamber 21 when the pressure `of air` within the tire shallhave become suiiciently reduced and to prevent the power of spring 82 acting to crush or injuriously affect the same by'causl ing thefair-chamberlto retract beyond the limit fixed by said stop.

The length of said ,stop-member isdesirspring 32' to a slight distance only below the v outer surface of the casing extremity so that ,outer vex-l after the disappearance of the tremity of the stem 26 from view or touch,

the stem can not travel any' farther nor. can

the air-chamber further contract.

It is believed that theoperation of my described pressure-indicating devices will be evident from the foregoing description. It may be stated, however, that it is the main object of said devices to indicate the lack'of o suiicient pressure within the tire and not t'o act necessarily'as a graduated gage to indicate-variations in the pressure above a predetermined minimumairfpressure. Therefore the stem 26 is unprovided with graduation marks but is fintended to protrude for a slight distance, as indicated in 'the views,

' under a normal'or suiicient pressure within the tire to maintain them in properly in- Hated condition. When such infi'ation,'how

lever, is reduc d beyond a safe minimum, and thestem recedes within the casing, vas may be indicated by sight or by the passingy of the hand over the end of the casing, it indicates`4 thatl the tire pressure is reduced beyond a safe minimum,rwhereupon the casing may be removedand the tire pressure increased in the usual manner. f

Among the advantages of my invention` are the simplicity of its construction, where- Lasagna .A

an indicator stem to permit the inward" /travel of said stem26 under the action of ed to be secured upon a the operating mechanism may be inclosed withina .cap or casing varying little from the ordinary cap now utilized for -inclosconvenience and ease with which the condif ascertained by, observation or by simply pressing the finger over the end of the casing to-determine the positionof the said stem 26.

claim, isf

1. lAn air pressure indicator including a' casing having one open end Aadapted to be secured to a tire valve shell'an'd hav-ing an aperturev through the other end thereof, a plug member having an axial bore therethrough-secured within said casing and adjustable longitudinally thereof, anexpansble and collapsible air chamber longitudinally movable within .said casing and having' an open end attached to the plug'member, longitudinally arranged. having one end supported by the other en of Asaid air'rchamber and having its other end normally extending into the aperture in the end ofthe casing, and a spring interposed 'between the .air

within said casin chamber and 'the second'named end of the longitudinally thereof, said plug member be.

ing provided with a fixed "transverse pin to engage the stem of atire valve in the shellto hold r in operativepostion, an expansible and collapsible air` chamber longitudinally 'movable within said casingA provided with means to limit the collapsingfthereof andhavng an open end attached tothe plug member, 'an

Having described my inventiojn, what I.l

ing the diend ofv thev tire valve; Aand the .60

tion of airepressure within the tire can'bel.

the same open wheny the indicator, is

indicator stem axiallyarranged within said casing having one end supportedA byJ the other end of said air chamber and' havingv its other vend nOrmally extending into the relatively small aperture in the end of the casing, anda spring interposed' between the air chamber and the lsecond named end ofl the casing to normally yieldingly hold the air chamber in collapsed position.

v -Signed at Seattle, Washingtong this-5th day of October, 1916. Y d y y v ROBERT Evans.

Witness: i

' E'. PE'rERsoN. 

